Process of electrodepositing a corrosion resistant nickel-chromium coating and products thereof



United. States Patent PROCESS OF ELECTRODEPOSITING A CORROSION RESISTANT NICKEL CHROMIUM COATING AND PRODUCTS THEREOF Thaddeus W. Tomaszewski, Dearborn, and Henry Brown,

Huntington Woods, Mich., assignors, by mesne assignments, to The Udylite Corporation, Warren, Mich., a corporation of Delaware No Drawing. Filed Mar. 1. 1963, Ser. No. 262,191

15 Claims. (Cl. 29194) This invention is for improvements in or relating to decorative nickel electroplating, and more particularly relates to (1) the electrodeposition of sub-microscopic satin textured to macroscopic stain textured fine-grained nickel plate from semi-bright and bright nickel plating baths containing dispersed therein fine bath-insoluble particles, and (2) to the exceptional corrosion resistance of these deposits when over-laid with a thin chromium plate.

The decorative fine-grained nickel deposits of this invention have various degrees of brightness, or of uniform smokiness, or of uniform satin-sheen depending mainly on the concentration and particle size of the dispersed fined powders in the semi-bright or bright nickel electroplating baths, the concentration of the nickel brighteners, the degree of agitation of the cathode or the solution, the brightness and smoothness of the metal surfaces plated upon, and the thickness of the plate applied, and these decorative nickel plates of various degrees of submicroscopic, microscopic, and macroscopic satin texture and luster when over-laid with a final thin chromium plate provide exceptionally outstanding corrosion protection to the underlying metal.

We have found that such improved decorative nickel deposits of this invention may be produced by the addition to semi-bright and bright nickel electroplating baths of water-insoluble fine powders of boron, silicon, and the borides of calcium, magnesium, tantalum, chromium, titanium, zirconium, vanadium, the carbides of chromium, vanadium, tungsten, and zirconium, the nitrides of silicon, titanium, and zirconium, and the silicides of titanium, zirconium, nickel, cobalt, and cerium, the phosphides of chromium, tungsten, molybdenum, manganese, nickel, cobalt, iron, cerium, titanium, zirconium and vanadium, and the oxides of thorium and stannic tin, including hydrated stannic oxide, (meta stannic acid).

These semiconductor-type powders of average particle size less than 5 microns and down to colloidal dimensions produce exceptionally highly corrosion resistant plate when given the usual final over-lay plate of about 0.01 mil (0.25 micron) of chromium plate. Even concentrations of th se fine powders of 0.05 to 0.2 grams/liter will make possible improved corrosion protection when the decorative plates obtained from these baths are given a final chromium plate of less than 0.2 mil (5 microns). Boron fine powder is exceptional in this respect. With most of these powders the maximum improvement in corrosion protection in the less accessible recessed areas of articles is attained when about to 50 grams/liter of the fine powders are dispersed in the nickel baths, and further increase in concentrations of powder until the baths become quite thick does not improve the already exceptional corrosion resistance when a final thin chromium plate is applied. When the higher concentrations of powder the plates become more satiny up to a point where further increase in concentration of powder produces no further change in appearance of the nickel plate at a given nickel plate thickness on a given base and with a given brightener concentration in the nickel bath. In some cases, as high as about 500 grams/liter of fine powder can be dispersed in the bath. Usually, about 250 grams/ liter of fine powder is the highest concentration ever "ice needed for the most macroscopic type of satin nickel plate.

The macroscopic stain textured types of nickel plate which can be obtained by using the higher concentratrons, e.g., about grams/liter or higher of the aforementioned powders in the semi-bright and bright nickel electroplating baths are fine-grained lustrous satin nickel deposits which not only have a very pleasing appearance, but which can also be high-lighted by buffing raised areas to give beautiful two-tone effects, and which when chromium plated with about 0.01 mil chromium plate will also provide exceptionally good corrosion protection to the basis metals such as ferrous, aluminum, magnesium, brass, copper, zinc and other metal articles.

The average particle diameter (herein sometimes referred to as particle size) of the finely powdered bathinsoluble materials should not be greater than 5 microns. As some roughness, especially on shelf areas where particles can settle, may result from the use of materials of particle size greater than about 5 microns, the use of material of particle sizes less than 5 microns are preferred and are advantageous, with the most preferred particle size averaging about 0.02 to about 3 microns as determined with the electron microscope. Some agglomerated particles may have larger particle size than 5 microns but with agitation in the nickel bath the larger agglomerates may be reduced to 5 microns and under. Agitation is usually necessary to keep the fine powder suspended in the baths during plating. Air agitation or mechanical agitation including ultra-sonic agitation of the baths can be used.

Analysis of a satin nickel plate from an air agitation bright nickel bath containing superfine powdered material of particle size of about 0.02 to 3 microns in concentrations even of about 100-200 grams/ liter shows usually not higher than about 2.5% of the powdered material uniformly distributed in the nickel plate, and with low concentrations of 10-20 grams/liter or lower of the finest powders, as low as about 0.01% to 0.03% by weight is present in the nickel plate. Microscopic examination of the surface of the plate shows an extremely uniform finely pitted surface which consists of micro-inclusions and micro-pits. Calculations and microscopic examinations indicate that the number of micro-inclusions and micropits per sq. cm. of surface is at least of the order of 10. This textured plate has excellent adhesion, for example, to nickel, ferrous, copper and brass surfaces similar to that obtained when the nickel bath contains none of the powdered material. The leveling of the bright nickel plate is not decreased by the presence of the finely powdered additives. The throwing and covering power of the agitated bright nickel baths with the suspended powders is about the same as without the fine powders present. It has been found that in plating articles with recessed areas and with shelf areas using particles of the preferred particle size, no objectionable roughness is obtained on the areas on which settling can occur, though in some cases with the larger particle sizes, the shelf areas may be somewhat duller than the rest of the article, though this is usually negligible with short plating times such as 30 seconds to about 5 minutes. With the microscopic satin nickel this dulling is, of course, no problem.

The fine bath-insoluble powders plate out as uniform dispersions in the semi-bright and bright nickel plate and thereby cause sub-microscopic (with the finest particles of 0.01 to about 0.05 micron size) to micro-inclusions and sub-microscopic to microscopic-pitting in the surface of the nickel plate. That is, at any given instant the surface of the semi-bright or bright nickel plate has distributed over its surface multitudinous fine particles in various stages of being imbedded in the surface and causing sub-microscopic and microscopic pitting, and with the thinnest plates (flashes or strikes) the pitting is mostly sub-microscopic becoming more microscopically visible with thicker plating. When the usual chromium plate of about 0.01 mil (0.25 micron) chromium is applied to these sub-microscopic to microscopic satin-textured surfaces a very fine favorable porosity pattern is developed in the chromium plate which is the key to the extraordinary corrosion protection afforded to the underlying metal by this composite nickel-chromium plate. With the very fine porosity pattern that is developed in the thin chromium plate there is obtained the very favorable condition of tiny cathode areas, the chromium surrounding the multitudinous tiny anodes (the sub-microscopic and microscopic pits) which results in very Weak corrosion currents with very low anodic current densities in the corrosive environments. Thus, the penetration of the corrosion pits toward the underlying basis metal is very greatly diminished. There is also some evidence of extremely fine stress-cracking of the chromium around the micro-inclusions which is also favorable to forming micro-cathodes and anodes. There is also the possibility that with the thin chromium plate where most of the micro-inclusions and micro-pits are not completely plated over, that the chromium in the micro-pits may have some chromium chromate inhibitor formed in the micropits which would, besides the poorly conducting particles, also be favorable to minimize the start of anodic attack. However, from the results obtained under prolonged severe corrosion exposure it is clear that it is the tiny cathode areas (chromium) surrounding the multitudinous tiny anode (nickel) areas that are responsible for the astounding corrosion protection afforded by the thin chromium plated sub-microscopic-to-macroscopic-textured fine-grained nickel deposits of this invention.

These textured nickel deposits give the best appearance and corrosion protection results when plated on top of semi-bright sulfur-free nickel or bright nickel deposits. It is best and also simpler to use the regular semi-bright or bright nickel plating baths for most of the plate and to use the minimum of the textured nickel plate required to obtain the desired appearance and corrosion resistance because the textured nickel plating bath requires added control due to the presence of the dispersed particles, and also because the best corrosion protection results are obtained in this way.

The mechanism by which the particles plate out is not completely understood, but it is thought that the adsorption of hydrogen ions and nickel ions by the particles would give the particles a positive charge and in this way they would tend to plate out. Under the powerful reducing conditions at the nickel cathode it may be possible that the particles which are not semi-conductors become semi-conductors by partial reduction. Irrespective of the mechanism of the plating out of these particles into the nickel plate, it is amazing how readily these particles plate out in a surprisingly uniform manner in semi-bright and bright nickel plates. The plating out of the fine particles starts immediately and in the bright nickel plating baths there is evidence that the first layers of nickel plated out actually contain somewhat higher concentrations of the fine powder than the subsequent ones. Also, the first layers may cause more micro-stress cracking in the thin chromium than the subsequent layers.

The macroscopic satin textured nickel plate obtained from the agitated bright or semi-bright nickel plating baths containing the higher concentrations of these fine powders can, as already mentioned, easily be buffed to a high luster, without losing the exceptional corrosion resistance when chromium plated. Thus, the beautiful two-tone effects achieved by buffing accessible portions of the macroscopic satin nickel plated object still have the very high corrosion resistance after final chromium plating. Another useful decorative effect can be obtained where brush or polishing lines are desired in a satin finish, by using coarse polishing grit, for example, 120 to 150 emery on the basis metal. The original coarse polishing lines, although diminished by the high leveling satin nickel plate, are still visible. In this way, a highly corrosion resistant scratch brush finish satin nickel is obtained without having to resort to scratch brushing a final nickel plate and thus greatly decreasing its corrosion protection.

Before technical grade powders are used commercially they should always be checked first in small scale tests such as in 1-4 liter baths before being added to large baths because certain harmful impurities such as metallic powders or too coarse particles may be present which will cause rough plate, especially on shelf areas, but otherwise technical grade fine powders normally produce results similar to those obtained from the use of high purity grades of the same particle size and structure. Also, if the powder is not wetted properly by the nickel bath, it should be washed with solvents and checked for freedom from fatty or oily films.

In general, bright or semi-bright nickel plating baths of the Watts, sulfate, high chloride, sulfamate or fluoborate type, or mixtures, can be used. While bori acid is the buffer usually used, other bufi'ers, such as formates, acetates, succinates or citrates may also be employed.

The pH of the baths may be from about 2 to 6, though the preferred pH values are from about 3.5 to 5.2. The temperature of the baths can be from room temperature to at least 80 0, though in general a temperature of about C. to about C. is preferred.

The best addition agents or brighteners to achieve the semi-bright and bright nickel plating conditions necessary to obtain the lustrous textured nickel after the addition to the bath of the afore-mentioned powders are the following: the sulfur-containing brighteners including aromatic and unsaturated aliphatic sulfonic acids, sulfonamides and sulfonimides, such as the benzeneor naphthalene-sulfonic acids, p-toluene sulfonamide, benzene sulfonamide, o-benzoyl sulfimide, vinyl sulfonic acid, allyl sulfonic acid, 2-butyne-l,4-disulfonic acid, o-sulfobenzaldehylde, etc; the addition agents which produce sernibright sulfur-free nickel plate such as formaldehyde, chloral hydrate, bromal hydrate, coumarin, butyne diol, adducts of butyne diol, used alone or in combination; combinations of unsaturated addition agents containing unsaturated linkages such as C C, C=N, CEC, CEN, with organic sulfur-containing brighteners, organic sulfon-compounds, and combinations of the latter with small concentrations of amines, such as quinaldine, polyamines and unsaturated amines such as N-allyl isoquinolinium bromide, or other quaternaries of pyridines or quinolines or isoquinolines.

Cobalt and iron can be present in the nickel bath as cobalt or ferrous sulfates, hlorides, bromides, sulfamates or fluoborates in concentrations as high as at least 40 grams/liter, yielding nickel alloy plates containing concentrations of cobalt and/or iron up to a total of about 50%, and it is to be understood that, except when the context requires otherwise, the expression nickel plate" as used herein covers such nickel alloy plates.

Surface active agents may be present in the baths, but are not usually necessary in the air agitated baths.

The maximum increase in lustrous sheen is obtained when the fine powders are used in the agitated full bright nickel plating baths such as the air-agitated bright nickel plating baths possessing good leveling properties. Less luster is obtained when the nickel baths contain only a carrier type brightener such as benzene or naphthaline sulfonic acids, p-toluene sulfonamide, benzene sulfonamide or obenzoyl sulfimide. In the latter cases the luster is flatter. This is also true when the semi-bright sulfurfree type of addition agent such as formaldehyde, coumarin, chloral hydrate or bromal, is used solely with the fine powders, and with these semi-bright addition agents it is usually best to use the ultra-fine particle size powders of less than 0.5 micron particle size and preferably less than 0.5 micron particle size as determined with the electron microscope.

The sub-microscopic to macroscopic satin textured nickel accepts chromium plate like regular nickel plate, and in general only the usual thicknesses of final chromium layer need be used, that is 0.25 micron though thicknesses of 2.5 or 5 microns may be used. Besides, the decorative nickel finish as such, or with the usual final chromium finish, the sub-microscopic to macroscopic satin textured nickel plate can be given a rhodium, silver, tin, brass, bronze, copper, gold, or tin-nickel (65-35) alloy or other final thin coating. Thin wax, or soluble wax, films or clear lacquers greatly decrease finger marking of the final coatings, such as nickel, bronze, silver, or brass coatings. Chromium, rhodium, and tin-nickel alloy plate do not need these organic coatings, at least not for tarnishing etfects.

Below are listed examples of baths of this invention. It is to be understood that other inorganic bath compositions may be used and other brighteners, though one of the preferred class of brighteners is the organic sulfoncompounds.

Example I Grams/liter Boron fine powder, 0.02 to 3 microns av. particle size 0.1-250 Ultra-fine silicon dioxide powder (Quso) 1-50 NiSO .6H O 200-300 NiCl .6H O 40-120 H 80 40 o-Benzoy1 sulfimide 1-4 p-Toluene sulfonamide 1-2 Allyl sulfonic acid 1-4 2-butynoxy-1,4-dietl1ane sulfonic acid 0.05-02 pH:3.5-5.2, temp. 50-70 C. Air agitation.

Example I! Silicon fine powder, 0.02 to 5 microns av.

particle size 0.2-150 NiSO .6H O 200-300 NiCl .6H O 40-80 H 80 40 Benzene sulfonamide 2-3 Allyl sulfonic acid 1-4 N-allyl quinaldinium bromide 0003-001 pH=3.5-5.2, temp. 50-70 C. Air agitation or mechanical agitation.

Example III Thorium oxide fine powder, 0.02 to 3 micron av. particle size 0.2-150 NiSO .6H O 50-200 NiCl bH O 200-100 H BO 40 Benzene sulfonamide 1-3 oBenzoyl sufimide 2-4 Allyl sulfonic acid l-3 N-allyl isoquinoliniurn bromide 0002-001 pH:3.0-5.2, temp. 50-70 C. Air agitation.

Example IV Titanium boride, 0.02 to 3 micron av. particle size 0.2-100 NiSO .6H 0 200-300 NiCl .6H O 40-120 H BO 40 o-Benzoyl sulfimide 1-4 Benzene sulfonamide 1-2 Allyl sulfonic acid 1-4 2-butynoxy-l,4-diethane sulfonic acid 0.05-0.2 pH=3.0-5.2, temp. 50-70 C. Air agitation.

6 Example V Boron fine powder, 0.02 to 3 micron av. particle size 0.02-5 Silicon dioxide fine powder, 0.02 to 0.5 micron av. ultimate particle size 10-50 NiSO .6H O 200-300 NiCI oI-I O 30-60 H B0 40 Bromal and/or chloral hydrate 005-01 Formaldehyde 0.02-0.08

pH:3.5-5.2, temp. 50-65 C. Air agitation or mechanical agitation When the ultra-fine particles of about 0.01 to 0.05 micron size particles are used in the semi-bright and bright nickel electroplating baths, it is difficult tosee the included particles in cross-sections of the nickel plate even at the highest magnification of the light microscope. However, on the surface of the plate using strong light it is possible to just see the microscopic pitting effect of these sub-microscopic particles. The thinner the plate that is deposited on a bright surface, the more difiicult is it to distinguish any difference between the appearance of the textured deposit and the bright plate obtained without the particles present. With increasing thickness of the deposit and with increasing concentrations of the fine particles, the micro-inclusions and micro-pitting can be more easily discerned, and an increasing degree of visible satin texture of the plate occurs. Thus, in the above examples of baths of this invention, the lower concentrations of powder of 0.02 to about 20 grams/liter, and in some cases even to about 50 grams/liter are best for obtaining bright plate from the bright nickel baths, and can thus be used best for very thin plates of about 0.01 to 0.1 mil thickness on top of regular bright nickel or semibright nickel plate to obtain after the final thin chromium plate very high corrosion protecting bright plate. Using the CASS and Corrodkote accelerated corrosion tests, many cycles are passed with only 0.6 mi] of regular bright nickel or semi-bright nickel that is given a thin plate (0.0] to 0.1 mil) from the baths illustrated in the above examples, and a final 0.01 mil chromium plate. Whereas, with regular bright nickel alone of the same total plate thickness and the same final thin chromium plate, not one cycle is passed, With the higher concentrations of powder and with thicker deposits (0.2 mil to 0.5 mil) the plate becomes more macroscopically satin-textured, and the extremely excellent corrosion protection is maintained when the same thin final chromium plate is applied. Again the best corrosion protection results are obtained when the textured plate of this invention is applied on top of regular nickel plate which can be dull, semi-bright or bright nickel plate depending on the decorative effect desired. That is, the degree of brightness, smokiness, or satin quality is dependent on the original brightness and smoothness of the surface plated upon, as Well as the thickness of the plate applied, the concentration and type of brighteners present, the concentration of the powder in the bath, the particle size of the powder and the type of powder, that is, its chemical constitution.

The nickel brighteners that produce very high leveling and brilliance as, for example, those given in US. 2,647,- 866 (August 4, 1953) and U8. 2,800,440 and 2,800,442 (July 23, 1957) will produce the highest brilliance with the powders dispersed in these bright nickel baths. For less luster, either the higher concentrations of the powders can be used in the very bright plating baths or lower concentrations or with just the organic sulfon-compounds present as brighteners. These latter brighteners such as o-benzoyl sulfimide, oor p-toluene sulfonamide naphthalene mono-, dior tri-sulfonic acids, etc., can be used in concentrations ranging from about 0.1 gram/liter to saturation.

In the case of barium, strontium and calcium stannates in the sulfate containing nickel baths such as the Watts nickel bath, there is also formed the insoluble sulfates of these alkaline earth metals from slight solubility of these stannates in the acidic bath. This effect is more predominant with barium and strontium and also with lead. However, this causes no problems in appearance effects or corrosion resistance results. Actually mixtures of fine powders give very good results. For example, cerium oxide or hydrated cerium oxide with stannic acids (hydrated stannic oxide), barium sulfate with stannic acids or stannic oxide, stannic oxide with fine silicon dioxide. With stannic oxide powder it is best to use about 1 to 50 grams/liter of very fine silicon dioxide. For example, with 0.02 to 1 gram per liter of stannic oxide it is best to use about -20 grams per liter of fine silica to obtain excellent sub-microscopic to microscopic textured [fully bright nickel plate from the bright nickel bath, and for macroscopic textured semi-bright nickel to use 1050 grams/liter of stannic oxide with 1 to 20 grams/liter of fine silica powder. By using these mixtures it is often possible to obtain the best distribution of the micro-inclusions and micro-pits in recessed areas where the plate is thinnest.

To achieve the highest possible corrosion protection results with the textured decorative nickel plate of this invention on complex shaped articles such as many zinc die-cast articles, for example, rear view mirror holders, intricate light housings, steel bumpers, hub caps, and grilles, it is best to use duplex or dual nickel underneath the textured nickel deposit. Thus, the total nickel deposit would consist of semi-bright sulfur-free nickel followed by regular bright nickel followed by a thin textured nickel deposit of this invention. The latter being used as thin plate (0.01 to about 0.1 mil) if the highest brilliance is desired, or as a thicker plate with more powder in the bath to obtain a more subdued brightness or satin type of finish if desired.

If between the semi-bright sulfur-free nickel and the regular bright nickel, a thin plate (0.02 to 0.1 mil) of higher sulfur-content (as nickel sulfide), nickel plate (0.1 to 0.2% sulfur) than the bright nickel plate, (005 to 0.08% sulfur) is used, then with this tri-nickel plate with a final textured nickel plate of this invention before the top thin chrominum plate, even the thinnest total nickel plate (0.3 mil) in deeply recessed articles stands up extremely well in very corrosive atmospheres. When ductile copper plate is used under nickel plate that has a final coating of the textured decorative nickel plate of this invention, then the copper plate also helps in the total corrosion resistance unlike the case when copper is used as a substitute for part of the bright nickel thickness in deposits of copper-bright nickel and the usual 0.01 mil thick final chromium. It is believed that this beneficial etfect of copper is also due to the tiny cathode areas developed in the final thin chromium plate, which in turn is due to the fine favorable porosity pattern developed in the thin final chromium plate as a result of its being deposited over a decorative nickel surface containing a rnultitudinous sub-micro to micro-inclusions and submicro to micro-pits of the order of 10 per sq. cm.

A particularly desirable and extremely corrosion resistant composite plate is formed by electroplating the nickel plate of this invention on the upper layer of the composite nickel coating described and claimed in copending application Ser. No. 103,296, filed Apr. 17, 1961, which is assigned to the assignee of this invention now US. Pat. No. 3,090,733, issued May 21, 1963. This composite plate comprises a lower nickel plate plate having an average thickness of about 0.15 mil to about 1.5 mils and an average sulfur content less than about 0.03%, a first overlying electroplate of nickel, or nickel-cobalt alloy containing at least about 50% of nickel and having a thickness of about 0.005 mil to about 0.2 mil and an average sulfur content of about 0.05% to about 0.3%, a second overlying layer of nickel or nickel-cobalt alloy containing at least about 50% nickel having a thickness of about 0.15 mil to about 1.5 mils and an average sulfur content of about 0.02% to about 0.15%, the second overlying layer containing a lower percentage of sulfur than said first overlying nickel electroplate and a higher percentage of sulfur than said lower nickel plate, an overlying layer of the nickel plate of this invention, and a top or upper layer of chromium having a thickness less than about 5 microns. In this composite plate, the fine grain nickel plate of this invention may vary from a thin flash layer to the thicker plate characterized as the macroscopic satin textured plate, but even the thin flash plates of this invention in such composite plate gives excellent corrosion resistance.

Boron very fine powder, and very closely next silicon and boron carbide very fine powders (0.02 to 2 or 3 microns) are extremely excellent and in many ways the best of the powders to use to obtain the highest corrosion protection over complex-shaped articles with deep recesses and just as long as the deep recesses can be chromium plated, the overall corrosion protection is excellent for the decorative plate. These three materials seem to behave as very similar semi-conductors as far as their plating out as micro-inclusions from the semi-bright and bright nickel plating baths is concerned.

It is thought that these varied types of materials function in a similar manner to produce the textured nickel electrodeposits of this invention because they all have the common property of being semi-conductors or becoming semi-conductors in the cathode film of the semi-bright and bright nickel plating baths.

What is claimed is:

1. A method for electrodepositing a decorative nickel plate which comprises the step of electrolyzing an aqueous acidic solution of at least one nickel salt selected from the group consisting of nickel sulfate, nickel chloride, nickel fluoborate, nickel sulfamate and mixtures of at least one said nickel salt with up to a total of about 40 grams/ liter of at least one salt selected from the group consisting of the sulfates, chlorides, fiuoborates and sulfamates of cobalt and iron, and at least one soluble organic addition agent capable of producing semi-bright to fully bright nickel plate, said solution containing dispersed therein about 0.1 to about 250 grams/liter of at least one material selected from the class consisting of boron and silicon, and the borides of calcium, magnesium, tantalum, chromium, titanium, zirconium and vanadium, the carbides of chromium, vanadium, tungsten and zirconium, the nitrides of silicon, titanium and zirconium, the silicides of titanium, zirconium, nickel, and cobalt, the phosphides of chromium, tungsten, molybdenum, manganese, nickel, cobalt, iron, titanium, zirconium and vanadium, and the oxides of stannic tin, said materials being in the form of a fine powder having an ultimate particle size of less than about 5 microns average diameter, thereafter piating on said electrodeposited layer an overlayer of a metal selected from the group consisting of chromium, rhodium, silver, tin, brass, bronze, copper, gold, and an alloy consisting of 65 tin and 35 nickel, said overlayer having a thickness in the range of about 0.25 to about 5 microns.

2. A method in accordance with claim 1 wherein said fine powder is boron.

3. A method in accordance with claim 1 wherein said fine powder is silicon.

4. A method in accordance with claim 1 wherein said fine powder is stannic oxide.

5. A method in accordance with claim 1 wherein said fine powder is metastannic acid.

6. A method for electrodepositing a decorative nickel plate which comprises the step of electrolyzing an aqueous acidic solution of at least one nickel salt selected from the group consisting of nickel sulfate, nickel chloride, nickel fiuoborate and nickel sulfamate and at least one soluble organic addition agent capable of producing semibright to fully bright nickel plate, said solution containing dispersed therein about 0.1 to about 250 grams/liter of at least one material selected from the class consisting of boron and silicon, and the borides of calcium, magnesium, tantalum, chromium, titanium, zirconium and vanadium, the carbides of chromium, vanadium, tungsten, Zirconium, the nitrides of silicon, titanium and zirconium, the silicides of. titanium, zirconium, nickei, and cobalt, the phosphides of chromium, tungsten, molybdenum, manganese, nickel, cobalt, iron, titanium, zirconium and vanadium, and the oxides of stannic tin, said material being in the form of a fine powder having an ultimate particle size of less than about 5 microns average diameter, thereafter plating on said electrodeposited layer an overlayer of a metal selected from the group consisting of chromium, rhodium, silver, tin, brass, bronze, copper, gold, and an alloy consisting of 65 tin and 35 nickel, said overlayer having a thickness in the range of about 0.25 to about 5 microns.

7. A method in accordance with claim 6 wherein the metal of said overlayer is chromium.

8. A method in accordance with claim 6 wherein said material is boron and said overlayer is chromium.

9. A method in accordance with claim 6 wherein said material is silicon and said overlayer is chromium.

10. A method in accordance With claim 6 wherein said material is stannic oxide and said overlayer is chromium.

11. A method in accordance with claim 6 wherein said material is metastannic acid and said overlayer is chromium.

12. A composite electroplate on a metal susceptible to atmospheric corrosion which comprises a nickel plate with a chromium overplate, said nickel plate having been electrodeposited from an acidic nickel plating bath containing dissolved therein at least one organic nickel brightencr capable of. producing semi-bright to fully bright nickel plate, and having dispersed in said bath in a concentration of about 0.1 to about 250 grams/liter of at least one type of bath insoluble particles of average ultimate particle size less than about 5 microns, an electrodeposited chromium overlay plate on said nickel plate of less than about 5 microns thickness, said particles in said nickel bath being selected from the group consisting of boron and silicon, and the borides of calcium, magnesium, tantalum, chromium, titanium, zirconium and vanadium, the carbides of chromium, vanadium, tungsten, and zirconium, the nitrides of silicon, titanium and zirconium, the silicides of titanium, zirconium, nickel, and cobalt, the phosphides of chromium, tungsten, molybdenum. manganese, nickel, cobalt, iron, titanium, zirconium and vanadium, and the oxides of stannic tin.

13. A composite electroplate in accordance with claim 12 wherein said nickel plate directly overlies an electro deposit consisting essentially of nickel.

14. A composite electroplate in accordance with claim 12 wherein said dissolved organic nickel brightener is selected from the group consisting of aromatic and unsaturated sulfonic acids, sulfonamides, and sulfonimides.

15. A composite electroplate on a metal surface susceptible to atmospheric corrosion which comprises a lower nickel electroplate having a thickness of about 0.15 mil to about 1.5 mils and an average sulfur content less than about 0.03%, a first overlying layer consisting essentially of an electroplate selected from the group consisting of nickel electroplate and nickel-cobalt alloy clectroplate containing at least about 50% nickel and having a thickness of about 0.005 mil to about 0.2 mil and an average sulfur content of about 0.05% to about 0.3%, a second overlying layer consisting essentially of an electroplate selected from the group consisting of nickel electroplate and nickel-cobalt alloy electroplate containing at least about 50% nickel, and having a thickness of about 0.15 mil to about 1.5 mils and an average sulfur content of about 0.02% to about 0.15%, the said second overlying layer containing a lower percentage of sulfur than the said first overlying nickel electroplate and a higher percentage of sulfur than said nickel plate, an overlying layer of nickel plate electrodepositcd thereon from an acidic nickel plating bath containing dissolved therein at least one organic nickel brightener capable of producing semibright to fully bright nickel plate and having dispersed therein about 0.1 to about 250 grams/liter of at least one material selected from the group consisting of boron and silicon, and the borides of calcium, magnesium, tantalum, chromium, titanium, zirconium and vanadium, the carbides of chromium, vanadium, tungsten, and zirconium, the nitrides of silicon, titanium and zirconium, the sili cides of titanium, zirconium, nickel, and cobalt, the phosphides of chromium, tungsten, molybdenum, manganese, nickel, cobalt, iron, titanium, zirconium and vanadium, and the oxides of stannic tin, and an electrodeposited overlayer of a metal selected from the group consisting of chromium, rhodium, silver, tin, brass, bronze, copper, gold, and an alloy consisting of 65 tin and 35 nickel, said overlayer having a thickness in the range of about 0.25 to about 5 microns.

References Cited by the Examiner UNITED STATES PATENT S 2,739,085 3/1956 McBride 204-181 X 2,771,409 11/1956 Cross 20440 X 3,057,048 10/1962 Hirakis 204-49 X 3,061,525 10/1962 Grazen 204-9 3,090,733 5/1963 Brown 204-4O 3,132,928 5/1964 Crooks et a1. 2044O X JOHN H. MACK, Primary Examiner.

HOWARD S. WILLIAMS, Examiner.

G. KAPLAN, Assistant Examiner. 

12. A COMPOSITE ELECTROPLATE ON A METAL SUSCEPTIBLE TO ATMOSPHERIC CORROSION WHICH COMPRISES A NICKEL PLATE WITH A CHROMOUM OVERPLATE, SAID NICKEL PLATE HAVING BEEN ELECTRODEPOSITED FROM AN ACIDIC NICKEL PLATING BATH CONTAINING DISSOLVED THEREIN AT LEAST ONE ORGANIC NICKEL BRIGHTER CAPABLE OF PRODUCING SEMI-BRIGHT TO FULLY BRIGHT NICKEL PLATE, AND HAVING DISPERSED IN SAID BATH IN A CONCENTRATION OF ABOUT 0.1 TO ABOUT 250 GRMS/LITER OF AT LEAST ONE TYPE OF BATH INSOLUBLE PARTICLES OF AVERAGE ULTIMATE PARTICLE SIZE LESS THAN ABOUT 5 MICRONS, AN ELECTRODEPOSITED CHROMIUM OVERLAY PLATE ON SAID NICKEL PLATE OF LESS THAN ABOUT 5 MICRONS THICKNESS, AND PARTICLES IN SAID NICKEL BATH BEING SELECTED FROM THE GROUP CONSISTING OF BORON AND SILICON, AND THE BORIDES OF CALCIUM, MAGNESIUM, TANTALUM, CHROMIUM, TITANIUM, ZIRCONIUM AND VANADIUM, THE CARBIDES OF CHROMIUM, VANADIUM, TUNGSTEN, AND ZIRCONIUM, THE NITRIDES OF SILICON, TITANIUM AND AIRCONIUM, THE SILICIDES OF TITANIUM, ZIRCONIUM, NICKEL, AND COBALT, THE PHOSPHIDES OF CHORMIUM, TUNGSTEN, MOLBYBENUM, MANGANSE, NICKEL, COBALT, IRON, TITANIUM, ZIRCONIUM AND VANADIUM, AND THE OXIDE OF STANNIC TIN. 